It is estimated that more than 25% of the general population in developed countries suffer from different degrees of functional dyspepsia and/or Irritable Bowel Syndrome, IBS. Such conditions are called for the purposes of this application, functional GI disorders. These disorders are clinical syndromes characterized by GI symptoms without identifiable cause. When a physiological cause is identified, these disorders are more correctly called organic dyspepsia or bowel disorders. The complex of dyspeptic symptoms is usually related to pain or discomfort generally felt in the center of the abdomen around or above the navel. Some examples of discomfort include fullness, early satiety, which is a feeling of fullness soon after starting to eat, bloating and nausea. There is no single organic disorder that explains all these symptoms, although about a third of all patients with these symptoms have delayed gastric emptying, though not usually so severe that it causes frequent vomiting. Additionally, a third also show a failure of the relaxation of the upper stomach following an ingestion of food, a condition known as abnormal gastric accommodation reflex. The prevalence of delayed gastric emptying in these patients is not significantly higher compared to asymptomatic individuals, but about half of the patients with these symptoms also have a sensitive or irritable stomach which causes sensations of discomfort when the stomach contains even small volumes. A gastric emptying study can show whether there is poor emptying of the stomach. Other motility disorders are more difficult to detect, but recently, there has been developed, as described for instance in “Practical Guide to Gastrointestinal Function Testing”, by C. Stendal, pages 194-201, published by Blackwell Science Ltd, Oxford, U.K., (1997), methods using an intragastric balloon connected to a computer-controlled pump called a barostat, which can show:    (a) distention or whether the upper stomach relaxes adequately during eating, and    (b) how much filling of the stomach it takes to cause pain or discomfort or gastric accommodation.
Barostat studies have shown the relation between dyspepsia symptoms and impaired accommodation by means of measuring stomach volumes as a function of intra-gastric pressure, or vice versa, and/or the symptomatic response to changes in intragastric pressure at different gastric volumes. In such barostat procedures, a liquid meal is administered, which can be either a high volume of water (up to 2 liters), an isotonic or high caloric value solution such as Ensure or Gatorade, a soup or a glucagon infusion. Then, for a given volume of the balloon, the pressure needed to induce gastric discomfort or pain is measured. This method is invasive, uncomfortable to the patient and impractical for wide clinical use. Furthermore, the barostat bag may interfere with gastric motility resulting in an inaccurate result. Another example of an organic cause of dyspepsia is a Helicobacter pylori infection.
Asymptomatic patients in risk groups such as diabetic patients, patients under drug therapy for Parkinson's Disease, and others, also benefit from investigations for determining specific GI disorders, which can affect the prognosis of their main diseases. For example, disturbed gastric emptying may affect the glycemic control in diabetic patients.
The stomach is generally described as being divided into two separate autonomic parts—the upper, proximal or fundus, and the lower, distal or antrum. The upper (proximal/fundus) stomach distends on the entry of food, as well as acting as a food reservoir and as a pump that pushes the liquids and gastric contents out of the stomach. The function of the lower (distal/antrum) stomach is to grind food down to smaller particles and mix it with digestive juices so that it can be absorbed when it reaches the small intestine. The stomach also empties its contents into the intestine at a controlled rate to avoid excessive delivery of food or acids, which could damage or overload the small intestine.
Three types of movements can generally be discerned in the stomach:    1. Rhythmic, synchronized contractions in the lower part of the stomach, at a rate of approximately 3 per minute, which create waves of food particles and juice which splash against the closed sphincter muscle (the pyloric sphincter) to grind the food down into small particles.    2. The upper part of the stomach shows slow relaxations lasting a minute or more that follow each swallow and that allow the food to enter the stomach maintaining constant pressure while volume is changing; at other times the upper part of the stomach shows slow contractions creating a gradient in pressure, which help to empty the stomach.    3. Between meals, after all the digestible food has left the stomach, there are occasional bursts of very strong, synchronized contractions that are accompanied by opening of the pyloric sphincter muscle. These are sometimes called “house-keeper waves” because their function is to sweep any indigestible particles out of the stomach. Another name for them is the migrating motor complex.
As previously mentioned, the barostat method is invasive, uncomfortable, impractical for wide clinical use, and may not necessarily provide accurate results. Furthermore, it is limited to determination of distension and filling disorders of the stomach alone, and other tests need to be applied for other disorders manifesting themselves in the GI tract, such as those generically related to transit time or malabsorption, or those called IBS disorders. The widespread prevalence of such gastric and GI malfunction makes it important to have a simple, quick, easily tolerable and reliable test for diagnosing and discriminating between various forms of such disorders.
The above-referenced book by C. Stendal is particularly useful as a review of the background of the subject matter of this application. The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.